1. Field of the Invention
The present invention relates to a single shaft punch press, including a machine frame, an eccentric shaft supported for rotation in the machine frame, a tool carrier guided for a rectilinear reciprocating movement in the machine frame, an arrangement of connecting rods having a plurality of connecting rod members drivingly mounted on the eccentric shaft, a lever means having a plurality of lever units, every lever unit having a first end and a second, opposite end, at which first end every lever unit is pivotally mounted to connecting rod members of the arrangement of connecting rods and at which second end every lever unit is pivotally supported at the machine frame, and every lever unit having a pivot member intermediate its first and second ends forming a further pivotal point, an arrangement of rams having a plurality of rams each having a first and a second, opposite end, which rams are pivotally mounted at their first end to a respective pivot member forming a further pivotal point of a respective lever unit, and at their second end to the tool carrier.
2. Description of the Prior Art
The off-center loading of the tools and tool carriers at single shaft punch presses, specifically the loading of the upper tool in such punch presses, causes a variety of difficulties and drawbacks. In a given frame size or machine size, respectively, the allowable loading of the tools decreases considerably towards the edge areas of the tools and reaches in certain cases even the value zero. Off-center loadings of the tools in punch presses cause a high wear and an increased friction specifically at bearings, e.g. between rams and tool carrier and also between rams and driving linkage members pivotally mounted thereto. An increased wear occurs also at the guiding structures of the rams and of the tools and also in tools themselves. Furthermore, off-center loadings cause also cogging or canting, respectively, and also elastic deformations such as, for instance, a deflecting of elongated structural members of the punch press and accordingly inaccurate products are produced.